An article formed from a brittle material, in particular a glass article, is required to be subjected to a secondary strengthening after a primary strengthening to ensure the edge strength. A conventional secondary strengthening employs HF chemical strengthening. In HF chemical strengthening, a glass is attached with acid-resistant films on both sides thereof and then soaked in a HF solution to be subjected to edge corrosion so that defects of edges thereof become smooth and therefore the edge strength of the glass is improved. However, the conventional wet-process HF chemical strengthening process has a high investment of equipment and a large floor area, the HF solution is prone to volatilize and cause damage to human bodies, and it is difficult to treat the HF waste liquid.